Children of mothers who take the antiepileptic drug valproate during pregnancy have lower IQ scores at age 6, a new study says. And the higher the dose of valproate during pregnancy, the greater the effect on a child's IQ, according to the report published in the Jan. 22 issue of The Lancet Neurology. For the study, the researchers looked at 305 pregnant women in the United States and United Kingdom who took a single drug to treat the seizure disorder -- either valproate (Depakote), carbamazepine (Tegretol), lamotrigine (Lamictal) or phenytoin (Dilantin).